The antonyms for the word "more knockout" would be words describing something less powerful or impressive. Some examples might include words like mundane, ordinary, unremarkable, or lackluster. Other possibilities could include words like undistinguished, mediocre, unimpressive, or dull. These antonyms indicate a lower level of intensity or excitement, and suggest that something is not particularly noteworthy or attention-grabbing. While "more knockout" might be used to describe something that is truly exceptional or outstanding, its antonyms suggest a more average or unexceptional quality.